This invention relates to novel herbicide formulations. In particular, this invention relates to novel aqueous flowable concentrates of the herbicide 2-(.alpha.-naphthoxy)-N,N-diethyl propionamide.
This herbicide, whose common name is "napropamide," and which is manufactured by Stauffer Chemical Company under the trademark DEVRINOL.RTM., has the following structural formula ##STR1## The synthesis and utility of this compound are disclosed in U.S. Pat. No. 3,480,671 (Tilles et al., Nov. 25, 1969), U.S. Pat. No. 3,718,455 (Baker et al., Feb. 22, 1973), and U.S. Pat. No. 3,998,880 (Mihailovski et al., Dec. 21, 1976).
Napropamide is a solid essentially insoluble in water and has been commercially available in the form of emulsifiable concentrates and wettable powders. The former is a solution of the herbicide and a surface-active compound in a water-immiscible or partially water-miscible solvent. When diluted with water, the solution forms an emulsion which is stabilized by the surface-active compound. Typical solvents for emulsifiable concentrates include mineral oils. petroleum products, chlorinated hydrocarbons, ethers, esters, and ketones. Unfortunately, a large amount of solvent is required, contributing substantially to the cost of the emulsifiable concentrate and accelerating the depletion of the natural resources from which the solvent was derived.
Wettable powders are water-dispersible powders containing the herbicide, an inert solid filler, and one or more surface-active agents to enhance wetting and prevent heavy flocculation when suspended with water. Typical solid fillers include natural clays, talcs, diatomaceous earth, and synthetic mineral fillers derived from silica and silicate. Unfortunately, it is difficult for the user to avoid contact with wettable powders during handling and mixing due to the dusty nature of the powders.
Flowable formulations, on the other hand, require little or no organic solvent and offer a greatly reduced possibility of user contact. Flowables are concentrated suspensions of a solid pesticide in an aqueous system. Having the characteristics of a thick liquid, a flowable formulation can be poured from a container, pumped, or otherwise transferred as any other viscous liquid. When the user is ready to apply the herbicide, he merely dilutes the flowable with water to the desired concentration and applies it to the field.
The optimum flowable formulation is one which demonstrates little or no settling and yet has a viscosity low enough to permit mixing and handling with reasonable ease. The optimum flowable will also have little susceptibility to syneresis whereby a thin liquid separates from the rest of the mixture, or to grit formation caused by the aggregation of the solid herbicide particles, particularly upon freezing and subsequent thawing of the suspension.
While various solid pesticides have been formulated as aqueous flowable concentrates, commercial preparations of napropamide have been mostly limited to emulsifiable concentrates and wettable poweders. It is therefore an object of this invention to provide an aqueous flowable concentrate of 2-(.alpha.-naphthoxy)-N,N-diethyl propionamide with little tendency to settle, little susceptibility to syneresis, and favorable freeze-thaw characteristics.
It is a further object of this invention to provide an aqueous flowable concentrate of 2-(.alpha.-naphthoxy)-N,N-diethyl propionamide, which is substantially homogeneous and thixotropic, in which the solid particles are substantially non-flocculated and have little or no tendency to settle to a hard cake upon standing which cannot be readily redispersed with mild agitation, and which dispenses spontaneously upon dilution with water.
A still further object of this invention is to provide a method of controlling undesired vegetation by applying to the locus where control is desired an aqueous dispersion of an herbicidally effective amount of 2-(.alpha.-naphthoxy)-N,N-diethyl propionamide formed by diluting the aqueous flowable concentrate of the present invention with water.
Further objects will be apparent from the following description.